Pivotal bone anchor with collet retainer and inner locking insert

ABSTRACT

A cervical polyaxial bone anchor includes a shank having an integral spherical head and a receiver having an upper channel for receiving a rod and a lower seat near a lower opening for receiving a closed retainer that includes a compressible upper portion engaged with the receiver seat and an expandable lower portion capturing the shank head. An outer sleeve slidable with the receiver prohibits expansion of the retainer lower portion during operation. A compression insert engages the retainer upper portion and is in friction fit with the shank head prior to fixing of an angle of the shank with respect to the receiver.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Ser. No.61/896,894, filed Oct. 29, 2013, which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

The present invention is directed to polyaxial bone anchors for use inbone surgery, particularly spinal surgery and particularly to such boneanchors with compression or pressure inserts and further includingretainers for capturing and retaining a bone screw shank head in thereceiver member assembly and later fixing the bone screw shank withrespect to the receiver assembly.

Bone screws are utilized in many types of spinal surgery in order tosecure various implants to vertebrae along the spinal column for thepurpose of stabilizing and/or adjusting spinal alignment. When vertebraeof the cervical spine are involved, the connecting structure orstructures commonly include a plate and cooperating relatively smallerscrews. When the connector is in the form of a rod, both closed-endedand open-ended bone screws are known with open-ended screws beingparticularly well suited for connections to rods and connector armsbecause such rods or arms do not need to be passed through a closedbore, but rather can be laid or urged into an open channel within areceiver or head of such a screw. Generally, the screws must be insertedinto the bone as an integral unit along with the head, or as apreassembled unit in the form of a shank and pivotal receiver, such as apolyaxial bone screw assembly.

Typical open-ended bone screws include a threaded shank with a pair ofparallel projecting branches or arms which form a yoke with a U-shapedslot or channel to receive a rod. Hooks and other types of connectors,as are used in spinal fixation techniques, may also include similar openends for receiving rods or portions of other fixation and stabilizationstructure.

A common approach for providing vertebral column support is to implantbone screws into certain bones which then in turn support a longitudinalstructure such as a rod, or are supported by such a rod. Bone screws ofthis type may have a fixed head or receiver relative to a shank thereof,or may be of a polyaxial screw nature. In the fixed bone screws, the rodreceiver head cannot be moved relative to the shank and the rod must befavorably positioned in order for it to be placed within the receiverhead. This is sometimes very difficult or impossible to do. Therefore,polyaxial bone screws are commonly preferred. Open-ended polyaxial bonescrews typically allow for a loose or floppy rotation of the head orreceiver about the shank until a desired rotational position of thereceiver is achieved by fixing such position relative to the shankduring a final stage of a medical procedure when a rod or otherlongitudinal connecting member is inserted into the receiver, followedby a locking screw or other closure. This floppy feature can be, in somecases, undesirable and make the procedure more difficult, but desirablein other situations.

SUMMARY OF THE INVENTION

An embodiment of the present invention is a bone screw assembly having ashank with an elongate body and a head with a radiused surface, theshank body being configured for fixation to a bone. The assembly furtherincludes a receiver having a top portion and a base with a substantiallycylindrical outer surface and a central axis of rotation. The receivertop portion defines a channel for receiving a longitudinal connectingmember. The base includes an internal seating surface partially defininga cavity, the top portion channel communicating with the cavity and thecavity communicating with an exterior of the base through a receiverlower opening. The assembly also includes a substantially cylindricalsleeve disposed about and closely receiving the receiver base. Thesleeve is axially slidable with respect to the receiver during assemblyof the shank with the receiver. A closed retainer cooperating with thereceiver and the shank head has a compressible upper portion illustratedwith upwardly extending slots, a central band or middle portion and anexpandable lower portion illustrated with downwardly extending verticalslots. The retainer upper portion has a first structure engaging thereceiver at the internal seating surface. The retainer lower portion isexpandable about the shank head and includes a second structure engagingthe sleeve to prohibit movement of the sleeve in an axial directionafter the shank head is captured by the retainer lower portion. Theretainer is attached to the receiver, but rotatable with respect to thereceiver prior to fixing of an angle of the shank with respect to thereceiver. A compression insert engages both the retainer upper portionand the shank radiused surface. In the illustrated embodiment, when theinsert is pressed downwardly into a friction fit engagement with theshank, the retainer upper portion resiliently holds the compressioninsert into such friction fit engagement with the shank head, allowingfor non-floppy pivoting of the shank with respect to the receiver uponthe use of some force. In some embodiments, the retainer lower portionincludes a cut-out for receiving a portion of the shank and thusproviding for an increased pivot angle of the shank with respect to thereceiver. Because the retainer can be rotated with respect to thereceiver prior to locking of the assembly in a final position, thelocation of the cut-out may be manipulated during surgery and thus alocation of an increased pivot angle of the shank with respect to thereceiver may also be manipulated as desired by the surgeon.

Objects of the invention include providing apparatus and methods thatare easy to use and especially adapted for the intended use thereof andwherein the tools are comparatively inexpensive to produce. Otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded and partial perspective view of a polyaxial bonescrew assembly according to an embodiment of the present inventionincluding a shank, a collet-like retainer, a receiver, an outer sleeveand a compression insert and further showing a cooperating rod andclosure top.

FIG. 2 is an enlarged top plan view of the shank of FIG. 1.

FIG. 3 is reduced and partial cross-sectional view taken along the line3-3 of FIG. 2.

FIG. 4 is an enlarged front elevational view of the receiver of FIG. 1.

FIG. 5 is a side elevational view of the receiver of FIG. 4.

FIG. 6 is a top plan view of the receiver of FIG. 4.

FIG. 7 is a bottom plan view of the receiver of FIG. 4.

FIG. 8 is an enlarged cross-sectional view taken along the line 8-8 ofFIG. 6.

FIG. 9 is an enlarged cross-sectional view taken along the line 9-9 ofFIG. 6.

FIG. 10 is an enlarged top plan view of the sleeve of FIG. 1.

FIG. 11 is an enlarged front elevational view of the sleeve of FIG. 10with portions broken away to show the detail thereof.

FIG. 12 is an enlarged perspective view of the retainer of FIG. 1.

FIG. 13 is an enlarged front elevational view of the retainer of FIG.12.

FIG. 14 is a top plan view of the retainer of FIG. 12.

FIG. 15 is a bottom plan view of the retainer of FIG. 12.

FIG. 16 is a cross-sectional view taken along the line 16-16 of FIG. 14.

FIG. 17 is an enlarged front elevational view of the insert of FIG. 1with portions broken away to show the detail thereof.

FIG. 18 is a top plan view of the insert of FIG. 17.

FIG. 19 is a bottom plan view of the insert of FIG. 17.

FIG. 20 is an enlarged front elevational view of the closure top of FIG.1 with portions broken away to show the detail thereof.

FIG. 21 is an enlarged front elevational view of the receiver and sleeveof FIG. 1 shown in a stage of assembly.

FIG. 22 is an enlarged front elevational view of the retainer and insertof FIG. 1 shown in a stage of assembly and with portions broken away toshow the detail thereof.

FIG. 23 is a front elevational view with portions broken away of thereceiver and sleeve of FIG. 21 and the retainer and insert of FIG. 22,the retainer being shown in a stage of assembly with the receiver.

FIG. 24 is a front elevational view with portions broken away, similarto FIG. 23 and showing the retainer in a subsequent stage of assemblywith the receiver.

FIG. 25 is a front elevational view with portions broken away, similarto FIG. 24 and showing the retainer in a subsequent stage of assemblywith the receiver wherein an upper portion of the retainer is capturedby the receiver.

FIG. 26 is a reduced perspective view with portions broken away of theassembly as shown in FIG. 25 and further shown with a dilation drivertool shown in partial perspective view.

FIG. 27 is an enlarged front elevational view with portions broken awayof the assembly and driver of FIG. 26 showing the driver in initialengagement with the retainer and the insert.

FIG. 28 is a front elevational view with portions broken away similar toFIG. 27 showing the driver pressing the insert upwardly into engagementwith inner surfaces of the upper portion of the retainer.

FIG. 29 is a front elevational view with portions broken away similar toFIG. 28 showing the driver subsequently further pressing the insert intoabutment with a ceiling surface of the receiver, the insert dilating theretainer upper portion until outer surfaces thereof are pressedoutwardly against a cylindrical surface of the receiver.

FIG. 30 is a reduced perspective view of the assembly of FIG. 29 afterthe dilation driver is removed and further showing the shank of FIG. 1just prior to assembly with the retainer, the shank shown in partialperspective view.

FIG. 31 is an enlarged front elevational view with portions broken awayof the assembly of FIG. 30 showing the shank in an initial stage ofassembly with the retainer.

FIG. 32 is a front elevational view with portions broken away, similarto FIG. 31 showing a head of the shank in a subsequent stage of assemblywith the retainer, pressing a lower portion of the retainer outwardly toa configuration of maximum expansion.

FIG. 33 is a front elevational view with portions broken away, similarto FIG. 32 showing the head of the shank pressed through the retainerlower portion and in engagement with the insert.

FIG. 34 is a front elevational view with portions broken away, similarto FIG. 33, showing the sleeve being lowered into a first stage ofengagement with the retainer.

FIG. 35 is a front elevational view with portions broken away, similarto FIG. 34, showing the sleeve in a subsequent stage of assembly withthe retainer, the sleeve pressing the lower portion of the retainerinwardly.

FIG. 36 is a front elevational view with portions broken away, similarto FIG. 35, showing an outer rim of the retainer being captured within agroove of the sleeve.

FIG. 37 is a reduced perspective view of the assembly of FIG. 36 furthershown with a shank driver.

FIG. 38 is an enlarged front elevational view of the shank driver ofFIG. 37 with portions broken away to show the detail thereof.

FIG. 39 is a top plan view of the driver of FIG. 38.

FIG. 40 is a bottom plan view of the driver of FIG. 38.

FIG. 41 is an enlarged front elevational view with portions broken awayof the assembly and driver of FIG. 37, the driver end being showninserted into a drive aperture of the shank upper portion or head.

FIG. 42 is a front elevational view with portions broken away, similarto FIG. 41, the driver being shown pressing the insert downwardly into afriction fit engagement with the shank head that in turn presses theshank downwardly into engagement with the retainer lower portion.

FIG. 43 is a front elevational view with portions broken away, similarto FIG. 42, the driver being shown being removed from the shank head andout of the receiver, leaving the shank head in non-floppy but movablefriction fit engagement with both the insert and the retainer.

FIG. 44 is an enlarged front elevational view with portions broken awayof the assembly of FIG. 43, showing the retainer rotated and the shankpivoted at an angle with respect to the retainer and insert with the useof some force.

FIG. 45 is an enlarged and partial perspective view of the assembly ofFIG. 44 illustrating a fifty-four degree angulation of the shank withrespect to the receiver.

FIG. 46 is a reduced perspective view of the assembly of FIG. 45 withthe shank being pivoted to a different position (thirty degree shankangulation with respect to the receiver).

FIG. 47 is a reduced perspective view of the assembly of FIG. 45 furthershown assembled with a portion of the rod (in phantom) and closure topof FIG. 1, also shown in perspective view.

FIG. 48 is another enlarged view of the assembly of FIG. 47 withportions broken away to show the detail thereof and shown with the shankinserted into bone.

FIG. 49 is an enlarged front elevational view of the assembly of FIG. 47wherein the shank was pivoted into a nominal or coaxial relation withthe receiver prior to assembly with the rod and closure top, and withportions broken away to show the detail thereof.

FIG. 50 is a side elevational view of the assembly of FIG. 49 withportions broken away to show the detail thereof.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is also noted that any reference tothe words top, bottom, up and down, and the like, in this applicationrefers to the alignment shown in the various drawings, as well as thenormal connotations applied to such devices, and is not intended torestrict positioning of the bone attachment structures in actual use.

With reference to FIG. 1, the reference number 1 generally represents apolyaxial bone screw apparatus or assembly according to an embodiment ofthe present invention that includes a shank 4 that further includes abody 6 integral with an upwardly extending upper portion or head-likecapture structure 8; a receiver 10; an outer sleeve 11; a closedcollet-like retainer structure 12; and a crown compression or pressureinsert 14. The receiver 10, sleeve 11, retainer 12 and compressioninsert 14 are initially assembled and may be further assembled with theshank 4 either by the vendor or prior to implantation of the shank body6 into a vertebra 17, as will be described in greater detail below. Insome embodiments, the shank could be implanted into a vertebra first,followed by assembly with the other components; however, in theillustrated embodiment of the assembly 1 that is sized and shaped foruse on the cervical spine, such a procedure is not preferred due to thesmall size of both the cervical vertebrae and the assembly 1. FIG. 1further shows a closure structure 18 for capturing a longitudinalconnecting member, for example, a 3.5 millimeter diameter rod 21 whichin turn engages the compression insert 14 that presses against the shankupper portion 8 into fixed frictional contact with the retainer 12, soas to capture, and fix the longitudinal connecting member 21 within thereceiver 10 and thus fix the member 21 relative to the vertebra 17. Theillustrated rod 21 is hard, stiff, non-elastic and cylindrical; however,it is foreseen that in other embodiments, the rod 21 may be elastic,deformable and/or of a different cross-sectional geometry. In someembodiments, the bone screw assembly 1 may also cooperate with softconnecting systems, such as spinal connectors having rigid sleeves forplacement within bone screw receivers in lieu of a rod, such sleevesincluding through bores for receiving a tensioned cord, for example. Thereceiver 10 and the shank 4 cooperate in such a manner that the receiver10 and the shank 4 can be secured at any of a plurality of angles,articulations or rotational alignments relative to one another andwithin a selected range of angles both from side to side and from frontto rear, to enable flexible or articulated engagement of the receiver 10with the shank 4 until both are locked or fixed relative to each othernear the end of an implantation procedure. The drawings at FIGS. 37-43also illustrate a driver, generally 24 for use with the assembly 1 aswill be described in greater detail below.

The shank 4, best illustrated in FIGS. 1-3, is elongate, the shank body6 being only partially shown in FIGS. 1 and 3. The body 6 is elongateand further includes one or more helically wound threads for boneengagement that are known in the art of pedicle screws, in particularsmaller screws sized and shaped for use on the cervical spine. Anexample of a larger pedicle screw shank for use with some embodiments ofthe invention is illustrated, for example, in U.S. Pat. No. 6,726,689,which is also incorporated herein by reference as an example of flangeform guide and advancement structures for use with receivers 10 andclosures 18 of embodiments of the invention. During use, the body 6utilizing the thread or threads (not shown) for gripping and advancementis implanted into the vertebra 17 (e.g., see FIG. 48) leading with a tipof the shank 6 and driven down into the vertebra with an installation ordriving tool (not shown), so as to be implanted in the vertebra to alocation at or near a neck thereof, as more fully described in theparagraphs below. The shank 4 has an elongate axis of rotation generallyidentified by the reference letter A.

A neck 26 extends axially upward from the shank body 6. The neck 26 maybe of the same or of a slightly reduced radius as compared to anadjacent upper end or top of the body 6 where the thread or threadsterminate. Extending axially and outwardly from the neck 26 is the shankupper portion or head 8 that provides a connective or capture apparatusdisposed at a distance from the threaded portion of the shank 6 and thusat a distance from the vertebra 17 when the body 6 is implanted in suchvertebra.

The shank upper portion 8 is configured for a fixed engagement betweenthe portion 8 and the retainer 12 and a pivotable connection between theshank 4 and the receiver 10 prior to fixing of the shank 4 in a desiredposition with respect to the receiver 10. The shank upper portion 8 hasan outer, convex and substantially spherical surface 34 that extendsoutwardly and upwardly from the neck 26 and terminates at an annular topor rim surface 38. The rim 38 may be planar, or as in the illustratedembodiment sloping downwardly and inwardly and towards the axis A. Thespherical surface 34 has an outer radius configured for frictionalsliding and then ultimate fixed cooperation with a concave surface ofthe compression insert 14 and concave surfaces of the retainer 12 aswill be discussed more fully in the paragraphs below. In someembodiments the top surface 38 may be substantially perpendicular to theaxis A. The spherical surface 34 shown in the present embodiment issubstantially smooth, but in some embodiments may include a rougheningor other surface treatment. The shank spherical surface 34 is lockedinto place exclusively by the insert 14 and the retainer 12 and not byinner surfaces defining the receiver cavity, the shank being held inspaced relation with the receiver by the retainer 12.

A counter sunk substantially planar base 45 partially defines aninternal drive feature or imprint 46. The illustrated internal drivefeature 46 is an aperture formed in the top surface 38 and generally hasa hex shape designed to receive a driving tool of an Allen wrench type,such as the driver 24, into the aperture for rotating and driving thebone screw shank 4. Each of the six faces of the drive 46 also includesa shallow indentation or groove that has a cylindrical surface 47 thatbegins at or near the rim 38 and terminates at a location spaced fromthe drive base 45. It is foreseen that the drive 46 tool engagementstructure may take a variety of tool-engaging forms and may include oneor more apertures of various shapes, such as a pair of spaced apartapertures or a multi-lobular or star-shaped aperture, such as those soldunder the trademark TORX, or the like. The seat or base surface 45 ofthe drive feature 46 is disposed substantially perpendicular to the axisA with the drive feature 46 otherwise being coaxial with the axis A. Thedrive seat 45 may include beveled or stepped surfaces that may furtherenhance gripping with the driving tool. In operation, a driving tool isreceived in the internal drive feature 46, being seated at the base 45and engaging the plurality of faces of the drive feature 46 for bothdriving and rotating the shank body 6 into the vertebra 17, eitherbefore the shank 4 is attached to the receiver 10 (in larger embodimentsuseful for thoracic or lumbar spine applications) or, as in the presentembodiment, after the shank 4 is attached to the receiver 10, with theshank body 6 being driven into the vertebra 17 with the driving toolextending into the receiver 10.

The shank 4 shown in the drawings is solid, but in some embodiments maybe cannulated, having a small central bore extending an entire length ofthe shank 4 along the axis A. Such a bore is typically defined by aninner cylindrical wall of the shank 4 having a circular opening at theshank driving tip and an upper opening communicating with the externaldrive 46 at the driving seat 45. Such a bore is typically coaxial withthe threaded body 6 and the upper portion 8. Such a bore provides apassage through the shank 4 interior for a length of wire (not shown)inserted into the vertebra 17 prior to the insertion of the shank body6, the wire providing a guide for insertion of the shank body 6 into thevertebra 17.

To provide a biologically active interface with the bone, the threadedshank body 6 may be coated, perforated, made porous or otherwisetreated. The treatment may include, but is not limited to a plasma spraycoating or other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

With particular reference to FIGS. 1 and 4-9, the receiver 10 has agenerally U-shaped appearance with various discontinuous and continuouscylindrical inner and outer profiles. The receiver 10 has a central axisof rotation B that is shown in FIG. 1 as being aligned with and the sameas the axis of rotation A of the shank 4, such orientation beingdesirable during assembly of the receiver 10, retainer 12 and insert 14with the shank 4. After the receiver 10 is pivotally attached to theshank 4, the axis B is typically disposed at an angle with respect tothe axis A, as shown, for example, in FIGS. 44-46.

The receiver 10 includes a base or lower body portion 60 that isillustrated as having a cylindrical outer surface, that in someembodiments may include other outer surface geometries, includingcurved, frusto-conical and partially planar. The base 60 defines a boreor inner cavity, generally 61, the base 60 being integral with a pair ofopposed upstanding arms 62 forming a cradle and defining a channel 64between the arms 62 with an upper opening, generally 66, the channelfurther defined by substantially planar interior arm surfaces 67 thatextend downwardly and transition to a U-shaped lower saddle or seat 68,the channel 64 having a width for operably snugly receiving the rod 21or portion of another longitudinal connector between the arms 62; thechannel 64 communicating with the base cavity 61.

Each of the arm interior surfaces 67 have formed or machines thereinvarious inner cylindrical profiles, an upper one of which is a partialhelically wound guide and advancement structure 72 located adjacent atop surface or rim 73 of each of the arms 62. In the illustratedembodiment, the guide and advancement structure 72 is a partialhelically wound interlocking flangeform configured to mate underrotation with a similar structure on the closure structure 18, asdescribed more fully below. However, it is foreseen that for certainembodiments of the invention, the guide and advancement structure 72could alternatively be a square-shaped thread, a buttress thread, areverse angle thread or other thread-like or non-thread-like helicallywound discontinuous advancement structures, for operably guiding underrotation and advancing the closure structure 18 downward between thearms 62, as well as eventual torquing when the closure structure 18abuts against the rod 21 or other longitudinal connecting member. It isforeseen that the arms could have break-off extensions.

With respect to the outer surfaces of the receiver 10, near each arm topsurface 73, an outwardly and downwardly extending frusto-conical surface75 transitions to an outer curved surface 76 that terminates at an outerdiscontinuous cylindrical surface 77, the surface 77 extends along amajority of each arm 62 and terminates at a curved, outwardly flaringsurface 78. The surface 78 terminates at a narrow cylindrical surface80. The surface 80 terminates at an overhang or ledge 82 that extendsinwardly to a cylindrical surface 84 that is contiguous with thecylindrical base 60. The cylindrical surface 84 has a diameter that isgreater than a diameter of the discontinuous cylindrical surface 80. Thecylindrical surface 80 has a diameter that is greater than a diameter ofthe discontinuous surface 77. The cylindrical surface 84 (as well as thecylindrical surface 80 and the surface 78) is discontinuous at and nearthe ledge 82, separated by the u-shaped channel 64 as well as by opposedthrough bores 86, each bore 86 located centrally in one of the arms 62and extending between the surfaces 78, 80, 82 and 84 at an outer openingthereof and the inner arm planar surface 67 at an inner opening thereof.The bores 86 may further include one or more curved or tapered surfaces87 that transition onto each arm outer surface. The opposed bores 86 maybe used with tools for holding the receiver 10 during assembly with theother components of the bone anchor and during implantation andmanipulation of the assembly 1 during surgery, for example. It isforeseen that other tool receiving grooves, depressions or apertures maybe configured in a variety of shapes and sizes and be disposed at otherlocations on the receiver arms 62. At the base 60, the cylindricalsurface 84 terminates at a bevel 88 that transitions to a planar annularbase bottom surface 90 that partially defines an opening, generally 91into the receiver cavity 61.

Returning to the interior surface 67 of the receiver arms 62, locatedbelow the guide and advancement structure 72 is a discontinuouscylindrical surface 94 partially defining a run-out feature for theguide and advancement structure 72. The cylindrical surface 94 has adiameter equal to or slightly greater than a greater diameter of theguide and advancement structure 72. Moving downwardly in a directiontoward the base 60, adjacent the cylindrical surface 94 of each arm is arun-out seat or surface 95 that extends inwardly toward the axis B andis substantially perpendicular to the axis B. In other embodiments, thesurface 95 may gently slope downwardly toward the axis B. Adjacent toand located below the surface 95 and formed in the planar surface 67 andthe saddle surface 68 of each arm in an area near and surrounding aboutthe through bore 86 is a shallow cylindrical surface 98 that terminatesat a ledge or ceiling surface 100 of each arm, the surface 100substantially perpendicular to the axis B and extending outwardly awayfrom the axis B. Extending downwardly from the ceiling surface 100 ofeach arm is another cylindrical surface 102 that is also discontinuous,being separated by the saddle portion 68 that partially forms thechannel 64. The cylindrical surface 102 of each arm terminates at adiscontinuous annular ledge or ceiling surface 103 that extendsoutwardly away from the axis B that in turn terminates at a cylindricalsurface 104 that extends below the u-shaped channel saddle 68 and thushas a continuous portion formed in the base 60 and thus underneath bothof the arms 62. The cylindrical surface 104 terminates at a continuousannular seating surface 106 that extends inwardly toward the axis B andis substantially perpendicular thereto. The surface 106 terminates atanother cylindrical surface 108. The cylindrical surface 104 has adiameter greater than a diameter of the cylindrical surface 102 and alsogreater than a diameter of the cylindrical surface 108. The surface 108diameter is greater than the surface 102 diameter. The cylindricalsurface 108 terminates at an outwardly flaring frusto-conical surface110 that terminates at the base surface 90, the surfaces 110 and 90forming the lower opening 91 of the receiver cavity 61.

With particular reference to FIGS. 1 and 10-11, the sleeve 11 that isreceived over the outer cylindrical surface 84 of the receiver at thebase 60 thereof is a substantially tubular structure having asubstantially uniform outer cylindrical surface 112, and innercylindrical surface 114, an annular and planar top surface 116 and anannular and planar bottom surface 118, the top and bottom surfaces 116and 118 both being substantially perpendicular to the outer and innercylindrical surfaces 112 and 114. In operation the sleeve 11 has thesame central axis of rotation B as the receiver 10. Near the bottomsurface 118 and adjacent to the surface 114 is an inner groove,generally 119, substantially defined by an outwardly and downwardlysloping surface 120, a cylindrical surface 122 and a bottom annularseating surface 124. The surface 124 terminates at a lower cylindricalsurface 126 having a diameter equal to the cylindrical surface 114. Thesurface 126 terminates at or near the bottom annular surface 118. In theillustrated embodiment, beveled surfaces are located on either side ofthe top surface 116 and on either side of the bottom surface 118. Theinner surfaces 120, 122 and 124 that define an inner cylindrical recessor groove 119 may also be connected by angled or beveled surfaces. Thesurfaces 120, 122 and 124 cooperate with an outer lip of the retainer 12as will be described in greater detail below. The diameter of thesurfaces 114 and 126 is slightly larger than a diameter of thecylindrical surface 84 of the receiver 10 so that the sleeve 11 isclosely, slidingly received by the inner surfaces 114 and 126 of thesleeve during assembly.

With particular reference to FIGS. 1 and 12-16, the rotatablecollet-like retainer 12 generally forms a closed ring but is expandableand contractible at both an upper portion and a lower portion thereofand thus may be described as having an upper resilient portion,generally 130, and a lower resilient portion, generally 132, bothportions integral with a central band, generally 134. Both portions 130and 132 have vertical slots and communicating cylindrical bores thatresult in key-hole-like openings that open upwardly for the portion 130and open downwardly for the portion 132 to provide for substantiallyindependent expandability and contractibility of both the upper andlower portions 130 and 132 with respect to the central band 134 duringvarious steps of assembly with the receiver 10, sleeve 11, shank 4 andinsert 14. The portions 130 and 132 and the central band 134 areintegral to one another, resulting in a one-piece retainer havingdiscontinuous surfaces that is also rotatably engaged to the receiver 10and pivotally engaged to the shank head 8 as will be described ingreater detail below. When assembled with the receiver 10, the retainer12 has a central axis C that is the same as the central axis of rotationB of the receiver 10. The upper portion 130 has outer structure forengagement with inner surfaces of the receiver 10 as will be describedin greater detail. The lower portion 132 has inner structure forcapturing the shank head 8 within the retainer central portion 134 andultimately fixing the shank head 8 against inner surfaces or edges ofthe lower portion 132. The lower portion further includes an outer lipthat engages the outer sleeve 11, the sleeve 11 providing a hard outerstructural support to the lower portion 132 preventing expansion of thelower portion 132 after the shank head 8 is positioned within theretainer 12 as will be described in grater detail below.

When in a neutral state, the retainer 12 has a substantially planar andannular discontinuous top surface 136 and an opposed and parallelsubstantially planar and annular discontinuous bottom surface 138. Thecentral band 134 includes a substantially cylindrical outer surface 140and a substantially cylindrical inner surface. Formed in the top surface136 and extending into the central band portion are six equally spacedvertical slots 144, each slot communicating with and terminating at acircular through bore 145 than runs between the surfaces 140 and 142 ofthe central band portion 134. The slots 144 run parallel to the centralaxis C of the retainer 12. The through bores 145 run radially toward theaxis C. Between each through bore 145 is an identically shaped throughbore 147 that communicates with a vertical slot 148 that runs downwardlytoward and through the retainer bottom surface 138. Thus, there are alsosix vertical slots 148 and six communicating through bores 147. Thevertical slots 148 of the lower portion 132 also run parallel to theaxis C and the through bores 147 run radially thereto. In theillustrated embodiment there are six upper slots 144 and communicatingthrough bores 145 and six lower slots 148 and communicating throughbores 147. However, it is foreseen that greater or fewer numbers ofslots and through bores may be used in other embodiments of theinvention, depending in part on the material used for the retainer 12which in the illustrated embodiment, preferred materials includetitanium alloy and cobalt-chrome alloy. Harder materials such as certaincobalt chrome alloys may require more slots and communicating key-holethrough bores than will softer, more resilient materials such astitanium, titanium alloy or stainless steel.

Returning to the retainer upper portion 130 that is sized and shaped toresiliently engage and fix to the receiver 10 as will be described ingreater detail below, the vertical slots 144 also extend through thefollowing outer surfaces of the portion 130: a frusto-conical outersurface 150 that is adjacent the top surface 136 and terminates at anouter cylindrical surface 152 having a lower circular edge 153; anannular ledge 154 that runs from the edge 153 of the outer cylindricalsurface 152 and terminates at another cylindrical surface 156, thesurface 156 having a diameter that is smaller than a diameter of thecylindrical surface 152; and an outwardly flaring curved surface 158that transitions to an annular surface 160 that terminates at themid-portion or band outer surface 140. The surfaces 160 and 154 are bothsubstantially perpendicular to the axis C when the retainer 12 is in aneutral position. The retainer surfaces 136, 152 and 154 are sized andshaped for sliding rotational engagement with the surfaces 103, 104 and106 as will be described in greater detail below. The retainer 12includes an inner cylindrical surfaces 162 running from the top surface136 to an inner bevel 163 that transitions radially outwardly to theinner band surface 142. The inner surfaces 162 is sized to closelyreceive an outer surface of the insert 14 during assembly as will bedescribed in greater detail below. All of the surfaces 150, 152, 154,156, 158, 160, 162 and 163 are discontinuous because the vertical slots144 run therethrough. The through bores 145 that communicate with theslots 144 as well as the through bores 147 that are formed in andthrough the outer and inner central band surfaces 140 and 142,respectively, also extend through a portion of the inner cylindricalsurface 162 and the bevel 163 as best shown in FIG. 16.

The retainer lower portion 132 is defined by the following featuresdescribed as they appear when the retainer 12 is in a neutral state: anouter discontinuous lip 166 that extends radially outwardly anddownwardly from the central band outer surface 140 and then transitionsinwardly to form a lower ledge surface 167 that terminates at acylindrical surface 169. When the retainer 12 is in a neutral state, thecylindrical surface 169 has a diameter that is the same or substantiallyclose to the diameter of the surface 140. The cylindrical surface 169extends to a lower inwardly radially extending discontinuousfrusto-conical surface 171 that terminates at the bottom surface 138.The outer lip 166 is sized and shaped to be ultimately received withinthe inner groove 119 of the sleeve 11. Adjacent the central band portioninner cylindrical surface 142, is a radially inwardly extending surface173 that terminates at an inner cylindrical surface 175, the surface 175being substantially parallel to the axis C when the retainer 12 is in aneutral state. A discontinuous circular edge 176 is formed by a junctureof the surfaces 173 and 175, the edge 176 ultimately is in lockedfrictional engagement with the spherical surface 34 of the shank head 8as will be described in greater detail below. The cylindrical surface175 terminates at a radially outwardly flaring frusto-conical surface177 that terminates at the bottom surface 183. Formed or cut-out of thelower surfaces 138, 171 and 177 and positioned centrally at a slot 148is a discontinuous curved surface 180 sized and shaped to receive aportion of the shank body 6 to provide for an extended angle of pivot asshown, for example in FIG. 45 and described in grater detail below. Theretainer lower portion 132 outer and inner surfaces 166, 167, 169, 171,173, 175, 177 and 180 are all discontinuous, being separated by the sixlower vertical slots 148 that each communicate with one of the throughbores 147. None of the through bores 147 extend downwardly into thelower portion 132. All of the through bores 145 and 147 are locatedsubstantially in the central portion or band 134 and include a smallupper part thereof partially located in the retainer upper portion 130.The bores 145 and 147 are evenly and uniformly aligned in a circle thatsurrounds the axis C and only differ from each other by a direction ofan opening thereof that communicates with either an upwardly ordownwardly directed slot 144 or 148.

With particular reference to FIGS. 1 and 17-19, the crown compression orpressure insert 14 is illustrated that is sized and shaped to bereceived by and down-loaded through the retainer 12 upper portion andtemporarily seated within the central band 134 prior to assembly of theretainer 12 upper portion 130 with the receiver 10 at the receiver loweropening 91. The compression insert 14 is sized and shaped to beultimately received in the retainer upper portion 130 as will bedescribed in greater detail below. The compression insert 14 has anoperational central axis that is the same as the central axis B of thereceiver 10. Prior to operation, the insert 14 may be advantageouslymanipulated downwardly into a friction fit with the shank head 8 whereinthe insert 14 frictionally engages the bone screw shank upper portionspherical surface 34, but is not locked against the portion 8, (i.e.,movement occurs when some force is applied) allowing for a non-floppymovement and placement of the shank 4 with respect to the receiver 10 ata desired angle during surgery prior to locking of the shank withrespect to the receiver near the end of the procedure.

The compression insert 14 is substantially cylindrical and tubular andincludes a planar annular top surface 183 and a planar annular bottomsurface 184, the surfaces 183 and 184 being perpendicular to the centralaxis of rotation. A radially outwardly extending frusto-conical surface186 begins at the top surface 183 and terminates at an outer cylindricalsurface 187. The surface 187 extends from the surface 186 to an outerbeveled surface 188 that transitions inwardly to the bottom annularsurface 184. An inner cylindrical surface 189 extends from the topsurface 183 and terminates at a radiused surface 190, the surface 190terminating at the insert bottom surface 184. The surface 190 issubstantially spherical and sized to closely receive and engage thespherical surface 34 of the shank head 8. Thus, a radius of the surface190 is approximately the same of substantially close to a radius of thespherical surface 34.

The surfaces 186 and 187 are sized and shaped to generally fit withinthe retainer inner band surface 142 and retainer top portiondiscontinuous inner surface 162. In a final operational position, theouter cylindrical surface 187 fits closely within the retainer innersurface 162 as will be described in more detail below.

The insert inner cylindrical surface 189 and spherical surface 190define a bore sized and shaped to receive the driver 24 therethroughthat engages the shank drive feature 46 during assembly and also whenthe shank body 6 is driven into bone with the receiver 10 attached.Also, the bore may receive other manipulation tools.

With reference to FIGS. 1 and 47-50, for example, the illustratedelongate rod or longitudinal connecting member 21 (of which only aportion has been shown) can be any of a variety of implants utilized inreconstructive spinal surgery, but is typically a cylindrical, elongatestructure having the outer substantially smooth, cylindrical surface ofuniform diameter. The illustrated rod 21 is sized for use on thecervical spine and thus has a diameter of 3.5 mm and may have a diameteras small as 3.0 mm. The rod 21 may be made from a variety of metals,including hard and soft metal alloys and hard and soft or deformable andless compressible plastics, including, but not limited to rods made ofelastomeric, polyetheretherketone (PEEK) and other types of materials.

In other embodiments, it is foreseen that longitudinal connectingmembers for use with the assembly 1 may take a variety of shapes,including but not limited to rods or bars of oval, rectangular or othercurved or polygonal cross-section. Some other embodiments may also beused with a tensioned cord. Such a cord may be made from a variety ofmaterials, including polyester or other plastic fibers, strands orthreads, such as polyethylene-terephthalate. Furthermore, thelongitudinal connector may be a component of a longer overall dynamicstabilization connecting member, with cylindrical or bar-shaped portionssized and shaped for being received by the compression insert 14 or thecompression insert of larger polyaxial screws for the thoracic or lumbarspine of a cooperating receiver having a U-shaped, rectangular- orother- shaped channel, for closely receiving the longitudinal connectingmember. The longitudinal connecting member may be integral or otherwisefixed to a bendable or damping component that is sized and shaped to belocated between adjacent pairs of bone screw assemblies, for example. Adamping component or bumper may be attached to the longitudinalconnecting member at one or both sides of the bone screw assembly. A rodor bar (or rod or bar component) of a longitudinal connecting member maybe made of a variety of materials ranging from soft deformable plasticsto hard metals, depending upon the desired application. Thus, bars androds may be made of materials including, but not limited to metal andmetal alloys including but not limited to stainless steel, titanium,titanium alloys and cobalt chrome alloys; or other suitable materials,including plastic polymers such as polyetheretherketone (PEEK),ultra-high-molecular weight-polyethylene (UHMWP), polyurethanes andcomposites, including composites containing carbon fiber, natural orsynthetic elastomers such as polyisoprene (natural rubber), andsynthetic polymers, copolymers, and thermoplastic elastomers, forexample, polyurethane elastomers such as polycarbonate-urethaneelastomers.

With reference to FIGS. 1, 20 and 47-50, the closure structure orclosure top 18 shown with the assembly 1 is rotatably received betweenthe spaced arms 62 of the receiver 10. It is noted that the closure 18top could be a twist-in or slide-in closure structure. The illustratedclosure structure 18 is substantially cylindrical and includes an outerhelically wound guide and advancement structure 192 in the form of aflange that operably joins with the guide and advancement structure 72disposed on the arms 62 of the receiver 10. The flange form utilized inaccordance with embodiments of the present invention may take a varietyof forms, including those described in Applicant's U.S. Pat. No.6,726,689, which is incorporated herein by reference. Although it isforeseen that the closure structure guide and advancement structurecould alternatively be a buttress thread, a square thread, a reverseangle thread or other thread like or non-thread like helically woundadvancement structure, for operably guiding under rotation and advancingthe closure structure 18 downward between the arms 62 and having such anature as to resist splaying of the arms 62 when the closure structure18 is advanced into the channel 64, the flange form illustrated hereinas described more fully in Applicant's U.S. Pat. No. 6,726,689 ispreferred as the added strength provided by such flange formbeneficially cooperates with and counters any reduction in strengthcaused by the small size of the cervical screw and longitudinalconnecting member. A single start flange form 192 is illustrated;however, it is foreseen the closure 18 may have two starts withcooperating flange form structure on the receiver arms 62. Theillustrated closure structure 18 also includes a top surface 194 with aninternal drive 196 in the form of an aperture that is illustrated as ahex-shaped internal drive, or may be, for example, a star-shaped or Torxdrive, or other internal drives such as slotted, tri-wing, spanner, twoor more apertures of various shapes, and the like. A driving tool (notshown) sized and shaped for engagement with the internal drive 196 isused for both rotatable engagement and, if needed, disengagement of theclosure 18 from the receiver arms 62. It is also foreseen that theclosure structure 18 may alternatively include a break-off head designedto allow such a head to break from a base of the closure at apreselected torque, for example, 30 to 60 inch pounds. Such a closurestructure would also include a base having an internal drive to be usedfor closure removal. The drive extends all the way through the closureto a bottom surface 198 of the closure and may include a rim or a pointand rim in some embodiments. The drive provides a cannulation throughbore extending along a central axis thereof and through the top andbottom surfaces thereof. Such a through bore provides a passage throughthe closure 18 interior for a length of wire (not shown) insertedtherein to provide a guide for insertion of the closure top into thereceiver arms 62 in some embodiments an methods.

In the illustrated embodiment, the receiver 10 is preferably made fromtitanium or titanium alloy as titanium is easier to machine than aharder material such as cobalt chrome. Also, the sleeve 11 helps toprovide strength and stability to the overall assembly 1. The sleeve 11,retainer 12 and crown insert 14 may each be made from a variety ofmaterials including cobalt chrome alloys, titanium and titanium alloys.

The two-piece driving tool 24 illustrated in FIGS. 37-43 for placing theinsert 14 into friction fit relationship with the shank head 8 and laterdriving the shank 4 into the vertebra 17 includes an innerplunger/driver 210 in slidable relationship with an outerholder/receiver engagement tool 212. The inner plunger/driver 210includes an upper holding potion that further includes a cylindricalholding portion 215 and a faceted end portion 217 having four sides anda square planar end surface 218. The cylindrical portion 215 is integralwith a lower cylindrical portion 220 having a diameter smaller than adiameter of the portion 215. The portion 220 terminates at a radiallyoutwardly extending lip 222 having an annular planar surface 223.Extending from the surface 223 is a hex-shape drive 224 having six facesand a planar tip or end surface 226. The drive 224 is sized and shapedto be closely received by the shank drive 46.

The outer holder 212 includes an annular planar end surface 228 adjacenta holding portion 230 that curves inwardly near a center thereof and issubstantially wider than the driver portion 215 diameter. In other wordsan outer diameter defined by the holding portion 230 is greater than thediameter of the portion 215. The portion 230 terminates at a lowerplanar annular surface 232. A cylindrical surface 234 extends downwardlyfrom the surface 232. The surface 234 has a diameter smaller than thediameter of the cylindrical portion 215. Near an end 236 of the portion234 a helically wound guide and advancement structure 238 is formed onthe portion 234 that is sized and shaped to helically mate with thereceiver helical guide and advancement structure 72. A cylindricalsurface 240 located below the guide and advancement structure terminatesat an annular end surface 241. The outer holder 212 is tubular having aninner cylindrical surface 244 running from the top end surface 228 tothe bottom annular surface 241, the surface 244 sized and shaped toclosely slidingly receive the inner plunger driver 210 at thecylindrical surface 220. Operation of the tool 24 will be described ingreater detail below.

With reference to FIGS. 21-36, the receiver 10, sleeve 11, retainer 12and insert 14 are preferably assembled at a factory setting thatincludes tooling for holding and alignment of the component pieces aswell as compressing or expanding upper and lower portions 130 and 132 ofthe retainer. In some circumstances, the shank 4 is also assembled withthe receiver 10, sleeve 11, retainer 12 and compression insert 14 at thefactory. In other instances, it may be more desirable for the surgicalstaff to pre-assemble a shank of a desired size and/or variety (e.g.,surface treatment of roughening the upper portion 8 and/orhydroxyapatite on the shank 6), with the receiver, sleeve, retainer andcompression insert. Allowing the surgeon to choose the appropriatelysized or treated shank 4 advantageously reduces inventory requirements,thus reducing overall cost. Although it may be possible to implant theshank 4 into a vertebra first, followed by pressing the retainer (thatis already attached to the receiver) over the shank, this may not bedesirable due to the extremely small size of the assembly 1 and the morefragile nature of the smaller cervical spine vertebrae for which theassembly 1 is designed.

Pre-assembly of the receiver 10 with the sleeve 11 is shown in FIG. 21.The outer sleeve 11 is placed below the receiver 10 as shown in theexploded view of FIG. 1 and the receiver base is dropped into the sleeveuntil the sleeve top surface 116 abuts against the overhang 82 locatedbeneath the cylindrical surface 80. The sleeve inner surface 114 is inslidable rotatable engagement with the receiver base outer surface 84.The sleeve 11 can also be slid axially downwardly off of the receiverbase 60 at this time.

Pre-assembly of the retainer 12 and the insert 14 is shown in FIG. 22.The insert 14 is inserted into the retainer 12 with the insert 14 bottomsurface 184 initially facing the retainer top surface 136. The insert 14is then dropped or moved within the retainer inner discontinuous surface162 and then the retainer inner central band surface 142 in a co-axialmanner until the bottom surface 184 of the insert 14 rests on theretainer lower portion inner surface 173 as shown in FIG. 22. Now theretainer 12 with captured insert 14 is ready to be assembled with thereceiver 10.

With reference to FIGS. 23-25, the retainer top surface 136 is movedinto the receiver opening 91 as shown in FIG. 23 with the retainer topouter frusto-conical surface 150 shown in initial engagement with thereceiver lower frusto-conical surface 110. The retainer upper portion130 is then compressed as shown in FIG. 24, preferably with the aid oftooling (not shown) so that the retainer outer surfaces 150, 152 and 156clear the receiver cylindrical surface 108 and inter into the receivercavity 61 partially defined by the cylindrical surface 104 and theannular seating surface 106. Compression of the upper portion 130 occursby pressing the upper portion radially inwardly causing a narrowing ofthe gaps or slots 144 and cooperating through bores 145 during pressingof the upper portion 130 in a radially inward direction toward the axisC. FIG. 24 shows the upper portion or collet 130 of the retainer 12 at astate of maximum compression. After the upper portion discontinuoussurface 154 is moved upwardly into the receiver and travels past thereceiver seating surface 106, the retainer 12 upper portion 130 isallowed to return to a neutral state that due the nature of the retainermaterial may not be the same as the original neutral state shown in FIG.22, for example, prior to the compression step of FIG. 24. As shown inFIG. 25, the illustrated retainer surface 152 is still somewhat slantedinwardly and is not parallel to the receiver cylindrical surface 104 asmight be expected and as might occur if the retainer 12 would have beenmade of a very resilient material. Even though the retainer upperportion 130 or collet is not in an original neutral position, theportion 130 has returned to a state wherein the upper collet portionannular ledge 154 is in contact with and captured by the receiverannular seating surface 106 from below and the receiver ceiling surface103 from above to an extent that the retainer 12 upper portion 130 isnow captured within the receiver cavity 61. It is foreseen that in otherembodiments of the invention, the retainer upper portion may beintroduced and fixed to the receiver in different ways, for example, theretainer and receiver may include helical threads and the retainer maybe rotated into threaded engagement with the receiver.

With reference to FIG. 26 a dilation tool is then used to position theinsert 14 at a desirable location within the retainer 12 for a next stepof assembly and also thereby press the retainer upper portion 130 outersurface 152 outwardly toward and against the receiver cylindricalsurface 104. For this purpose, a dilation tool 260 of which only aportion is shown is used. The dilation tool includes a partiallyspherical driving surface 262 that transitions to a cylindrical holdingsurface 264. The tool 260 is sized and shaped to be slidably receivedinto the retainer lower portion 132 at the surface 175 and the drivingsurface 262 has a radius that is the same or substantially similar to aradius of the compression insert surface 190. It is foreseen that thetool 260 may be part of a larger robotic apparatus that would includetooling for holding the receiver 10 at the opposed through bores 86(and/or other locations along the receiver) and also, if needed, forholding the sleeve 11 out of the way of the retainer lower portion andin the desired location shown in FIG. 26. The tool 260 is inserted intothe lower portion 132 of the retainer 12 with the forward surface 262initially moving past the retainer surface 175 that defines a loweropening of the retainer 12 and into engagement with the lower sphericalsurface 190 of the compression insert 14. With reference to FIGS. 27 and28, the tool 260 is moved upwardly in a direction toward the receiverarms 62 and pushes the insert 14 generally upwardly and thereby pushesthe insert outer frusto-conical surface 186 into engagement with theresilient discontinuous surface 162 of the retainer upper portion 130,the insert 14 pressing the retainer upper portion 130 outwardly as thefrusto-conical surface 186 moves upward and the larger diameter insertcylindrical surface 187 comes into engagement with the retainer innersurface 162 as shown in FIG. 28. With reference to FIG. 29, the tool 260continues to press the insert 14 upwardly until the insert top surface183 abuts against the receiver ceiling surface 100. At this time, theinsert outer cylindrical surface 187 has pressed the retainer upperportion 130 outwardly to a maximum expanded position within the receiver10 wherein the retainer outer cylindrical surface 152 is in engagementwith the receiver inner cylindrical surface 104. The tool 260 is thenpulled away from the insert lower surface 190 and removed from theretainer 12 lower portion 132.

With reference to FIG. 30, at this time, the receiver, sleeve, insertand retainer combination is ready for assembly with the shank 4 at thefactor or, alternatively, for shipping to an end user (e.g., surgicalstaff) who will thereafter assemble the combination with a desired shank4. As shown in FIG. 39 the shank axis A and the receiver axis B arepreferably aligned during assembly as shown in FIGS. 30-36. It is notedthat although the retainer 12 upper portion is fixed to the receiver 10with respect to axial or up and down movement along the receiver axis B,the retainer 12 may be rotated with respect to the receiver 10 about thereceiver axis B. After assembly with the shank 4, but before insertionof a rod and closure top, the insert 14 may be placed into friction fitengagement with the shank head 8 as shown in FIGS. 37-43 and thereceiver 10 may be placed at a desired angle with respect to the shank 4as shown, for example, in FIGS. 44-46.

Returning to FIGS. 30-36, the shank 4 is assembled with the retainer 12as follows: With reference to FIG. 30, the shank is positioned beneaththe retainer lower portion 132 with the shank head 34 facing theretainer 12 outer lower surface138 and the spherical surface 34 is thenpressed against the retainer lower surface 177 as shown in FIG. 31. Withreference to FIG. 32, the resilient retainer lower portion 132 ispressed radially outwardly at the surface 175 as the shank head 8 ismoved upwardly toward the insert 14. With reference to FIG. 33, theshank head 8 is pressed upwardly into engagement with the insertspherical surface 190 and a hemisphere of the surface 34 passes throughthe most narrow opening of the retainer defined by the retainerdiscontinuous surface 175, the resilient lower portion 132 returning toa near neutral state capturing the shank head 8 therewithin. Withreference to FIG. 34, the outer sleeve 11 is then moved downwardlytoward the retainer outer lip 166, the sleeve inner surface 114 slidingalong the retainer surface 140 and pressing the retainer lower outersurface 140 inwardly, thereby pressing the retainer lower portion 132into an original neutral state and prohibiting an subsequent expansionof the lower portion 132. With reference to FIGS. 35 and 36, the sleeve11 is pressed further downwardly along the surface 149 until theretainer lip 166 is received in the sleeve inner groove defined by thesleeve surfaces 120, 122 and 124. With reference to FIG. 36, at thistime, the sleeve 11 is fixed axially with respect to the retainer lowerportion 132, the retainer lip 166 closely received by the sleeve slopingsurface 120, inner cylindrical surface 122 and bottom seat 124. Anyupward force placed on the sleeve 11 causes the lip lower ledge 167 toabut against the sleeve groove bottom seat 124. The sleeve lower innercylindrical surface 126 is now fixed axially into position facing theretainer lower cylindrical surface 169. It is noted that such axialfixing of the sleeve 11 with respect to the retainer 12 does notprohibit the retainer 12 from rotating with respect to the receiver 10about the receiver axis B.

With reference to FIGS. 37-43, the driving tool 24 may then be used topush the insert 14 down toward the receiver base or bottom 90 to anextent that an engagement between the insert surface 190 and the shankspherical surface 34 is a non-locking friction fit. Such friction fitengagement allows for non-floppy pivoting movement of the shank 4 withrespect to the retainer 12 (and thus with respect to the receiver 10)with some force and such temporary desired angular orientation will holdin place during surgery until ultimately frictionally locked in placenear an end of the surgical procedure. Thus, with reference to FIG. 37,the driver 24 is inserted into the receiver upper opening 66 with thetool hex driver 224 directed toward the shank internal drive 46. Withreference to FIG. 41, the hex driver 224 is inserted until the drivertip 226 engages the shank internal drive base surface 45. With referenceto FIG. 42, the driver outer holder 212 is then slid downwardly alongthe inner drive cylindrical surface 220 until the guide and advancementstructure 238 comes into engagement with the receiver guide andadvancement structure 72. The outer holder 212 is then rotated so thatthe guide and advancement structure 238 helically mates with the guideand advancement structure 72 of the receiver 10. As the outer tool 212is rotated, the outer tool end surface 241 abuts against the driver lip222 pressing the driver lip bottom surface 223 downwardly against theinsert 14 top surface 183 and also pressing the driver tip 226downwardly against the shank drive seat 45 thus pressing the shank head8 downwardly against the inner upper edge 176 of the surface 175 of theretainer lower portion 132. As shown in FIG. 43, when the outer drivetool is rotated in reverse to unscrew the guide and advancementstructure 238 from the receiver flange form 72 and the driver 225 isremoved from the shank internal drive 46, the insert 14 is retained in afriction fit engagement with the shank head surface 34 because theinsert outer surface 187 is in a fixed frictional engagement with theretainer upper portion discontinuous inner surface 162.

With reference to FIGS. 44-46, at this time, the receiver 10 may bearticulated to a desired angular position with respect to the shank 4prior to insertion of the rod 21 or closure top 18, that will be held,but not locked, by frictional engagement between the insert 14 (that isnow locked against the retainer 12) and the shank head spherical surface34. FIG. 44 illustrates a fifty-four degree sagittal plane angulation ofthe shank 4 with respect to the receiver 10 with the shank body 6received in the retainer cut-out 180. FIG. 44 illustrates anotherfifty-four degree angulation of the shank 4 with respect to the receiver10, but wherein the retainer 12 has been rotated with respect to thereceiver 10 about the receiver axis B to an arbitrary location desiredby a surgeon that will hold in such non-locked but also non-floppyposition by the friction fit engagement between the insert 14 and theshank head 8 until moved by force to another orientation. FIG. 46illustrates an alternative thirty degree angular position of the shank 4with respect to the receiver 10 showing the shank body 6 pivoted awayfrom the retainer cut-out 180.

The assembly 1 made up of the assembled shank 4, receiver 10, sleeve 11,retainer 12 and compression insert 14, is screwed into a bone, such asthe vertebra 17, by rotation of the shank 4 using a suitable drivingtool, such as the tool 24, for example, that operably drives and rotatesthe shank body 6 by engagement thereof at the internal drive 46. Inother embodiments of the assembly 1 of the invention, for example, foruse with the thoracic or lumbar spine wherein the bone screw shank 4 isrelatively larger, the shank 4 may be cannulated. In some procedures,the vertebra 17 may be pre-drilled to minimize stressing the bone andhave a guide wire (not shown) inserted therein to provide a guide forthe placement and angle of the shank 4 (in embodiments wherein the shankis cannulated) with respect to the vertebra. A further tap hole may bemade using a tap with the guide wire as a guide. Then, the assembly 1may be threaded onto the guide wire utilizing the cannulation bore. Theshank 4 is then driven into the vertebra using the wire as a placementguide. It is foreseen that the shank and other bone screw assemblyparts, the rod 21 (also having a central lumen in some embodiments) andthe closure top 18 (also with a central bore) can be inserted in apercutaneous or minimally invasive surgical manner, utilizing guidewires. In other larger embodiments, the shank 4 may be driven into thevertebra 17 without the remainder of the assembly 1 and the assembly 1is then pressed onto the shank head 8. In such embodiments, the shank 4may either be driven to a desired final location or may be driven to alocation slightly above or proud to provide for ease in assembly withthe pre-assembled receiver, compression insert and retainer.

With reference to FIGS. 47-50, in the illustrated embodiment, the rod 21is eventually positioned in an open or percutaneous manner incooperation with the at least two bone screw assemblies 1. The closurestructure 18 is then inserted into and advanced between the arms 62 ofeach of the receivers 10. The closure structure 18 is rotated, using atool engaged with the inner drive 196 until a selected pressure isreached at which point the rod 21 engages the top surface 183 of thecompression insert 14, pressing the insert surface 190 into lockedfrictional engagement with the shank spherical surface 34. The insert 14also urges the shank upper portion 8 toward the retainer edge surface176 and into locking engagement therewith, the retainer 12 frictionallyabutting and expanding outwardly against the sleeve 11. FIGS. 47 and 48show the assembly one in such a locked position wherein the shank 4 hadbeen previously pivoted with respect to the receiver to a fifty-fourdegree angle with the shank body 6 received in the retainer cut-out 180.FIGS. 49 and 50 show the assembly 1 in a locked position with the shank4 axially aligned with the receiver axis B.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

1. A receiver assembly of a pivotal bone anchor for securing a rod to ashank head via a closure top, the receiver assembly comprising: areceiver having a longitudinal axis, a base defining an internal cavitycommunicating with a bottom surface of the base through a distalopening, and a pair of integral arms extending upward from the base todefine an open channel, the open channel communicating with the internalcavity to define a receiver bore centered about the longitudinal axis,the receiver bore having at an internal recess formed therein; aretainer having an upper portion with a discontinuouscircumferentially-extending lateral protrusion, a lower collet portionconfigured to receive and snap around the shank head uploaded through alower collet opening, and a retainer bore extending between a retainertop surface and the lower collet opening, the lateral protrusion beingresiliently snapped into the receiver bore internal recess with theretainer bore coaxial with the receiver bore; and an inner insertconfigured for uploading into the retainer through the lower colletopening and upward through the retainer bore to the retainer upperportion prior to uploading the shank head, the inner insert having a topsurface engageable with the rod, wherein after the retainer lateralprotrusion is captured within the receiver internal recess, the innerinsert is downwardly movable within the retainer bore to engage theshank head snapped into the retainer lower collet portion.
 2. Thereceiver assembly of claim 1, wherein the pressure insert includes acentral bore for receiving a driving tool therethrough.
 3. The receiverassembly of claim 1, wherein the retainer lower collet portion furthercomprises a plurality of slots extending upwardly from the lower colletopening to a plurality of apertures extending radially through a middleportion of the retainer.
 4. The receiver assembly of claim 1, whereinthe retainer lower collet portion is engageable with the shank head whenthe shank head is inserted into the retainer so as to space the shankhead from the sidewalls of the receiver internal cavity.
 5. The receiverassembly of claim 1, wherein the retainer lower collet portion furtherincludes an interior contact surface extending inwardly to slidablyfrictionally engage a lower portion of the shank head.
 6. The receiverassembly of claim 1, wherein a bottom surface of the pressure insert isconfigured to engage the shank head radiused surface in a friction fitengagement.